1. Field of the Invention
The present invention relates to a damper for a speaker whose neck portion is formed of a plurality of dampers, and a method of producing the same.
2. Description of the Related Art
FIG. 7 shows a general structure of a speaker provided with a damper. The damper for supporting a vibration system of the speaker as shown in FIG. 7 generally has a number of corrugations 75 concentrically formed on the damper 74.
In FIG. 7, numeral 71 represents a speaker body, and 72 represents a magnetic circuit. The magnetic circuit 72 consists of a yoke 76, a center pole 77, a magnet 78, and a top plate 79. Numerals 80, 81, and 82 represent a frame, a diaphragm, and a coil bobbin respectively.
Usually, the damper 74 is molded by impregnating a material for the damper 74 with a thermosetting resin, and then, hardening the thermosetting resin by a heating press into a shape of the damper.
However, in the damper produced through the above process, there often occurs a problem of so-called neck break that a fabric is broken at a joint between the coil bobbin 82 and the damper 74, when a high power such as subwoofer is supplied.
Recently, as a countermeasure for such neck break, there has been employed a dual damper whose neck portion is molded of two sheets of dampers. By thus doubling the neck portion, a load on the neck portion will be dispersed, and as the results, the neck break will hardly occur.
This dual damper can be manufactured as shown in FIGS. 8A, 8B and 8C, by provisionally molding a fabric impregnated with a thermosetting resin as an auxiliary damper 92 (FIG. 8A), by applying or impregnating a thermosetting adhesive to the auxiliary damper 92 which reinforces the neck portion, after shaping a periphery of the auxiliary damper 92 (FIG. 8B), and by molding the auxiliary damper 92 simultaneously with a primary damper 91 to bond them to each other (FIG. 8C).
The thermosetting adhesive has been employed for the reason that the thermosetting resin is suitable for molding the damper into an appropriate shape, and particularly, the thermosetting adhesive is low in a unit price.
The above described dual damper has had a drawback that mass production has been difficult, because an additional step of applying the adhesive has been required in the production process.
There has been another drawback that because the adhesive is applied to the damper containing fibers, the adhesive may leak out through seams, and as the results, molds may be soiled when molding. Moreover, in order to improve point bonding between the fibers, directions of the seams must be aligned, when boding the fibers to one another, thus incurring bad workability.
Further, in case of a damper having a molding clearance such as an electrically conductive damper or the like, the thermosetting adhesive is difficult to be applied, and due to viscosity of the adhesive, an irregular adhesion may occur, resulting in an abnormal noise such as a rattle. In addition, the auxiliary damper must be attached to the primary damper concentrically so as not to disturb movements of the damper, and for this reason, the periphery of the auxiliary damper must be cut before bonding.
The present invention has been made in view of the above described circumstances, and its object is to provide a damper for a speaker and a method of producing the same in which reliability of the damper in resisting a high power will be enhanced, by molding the neck portion with a plurality of dampers consisting of a primary damper and an auxiliary damper. It is a further object of the invention to provide a damper for a speaker and a method of producing the same in which by employing a laminate film or a coating agent adjustable in thickness when bonding the auxiliary damper to the primary damper, they can be bonded irrespective of the seams, an irregular adhesion can be avoided, and the molds are less soiled. A still further object of the invention is to provide a damper for a speaker and a method of producing the same in which by simultaneously molding the auxiliary damper and the primary damper, production steps are reduced in number, variation in the production can be eliminated, manufacturing cost will be reduced, and at the same time, an anti-vibration effect can be expected.
In order to solve the above described problems, there is provided, according to the present invention, a damper for a speaker comprising an auxiliary damper impregnated with a thermosetting resin, a laminate film laminated on the auxiliary damper, and a primary damper formed on the auxiliary damper or the laminate film.
Because the laminated film is allowed to melt and bonded to the auxiliary damper, the auxiliary damper can be bonded to the primary damper irrespective of the seams, and it will be possible to provide the damper for a speaker which is produced with enhanced workability, and at the same time, free from an irregular adhesion. It is a further effect of the invention that the molds will be less soiled, as compared with the conventional case in which the adhesive has been used.
According to a second aspect of the present invention, there is provided a damper for a speaker comprising an auxiliary damper impregnated with a thermosetting resin and coated with a coating agent, and a primary damper formed on the auxiliary damper or the coating agent.
Because the coating agent is allowed to melt and bonded to the auxiliary damper, the auxiliary damper can be bonded to the primary damper irrespective of the seams, and it will be possible to provide the damper for a speaker which is produced with enhanced workability, and at the same time, free from an irregular adhesion. It is a further effect of the invention that the molds will be less soiled, as compared with the conventional case in which the adhesive has been used.
According to another aspect of the invention, the auxiliary damper is composed of a plurality of sheets.
As the results, reliability of the damper in resisting a high power at the neck portion can be enhanced, and the damper can be produced at a low cost without variation in the production.
According to still another aspect of the invention, there is provided a method of producing a damper for a speaker comprising the steps of laminating a film on an auxiliary damper which has been impregnated with a thermosetting resin, and bonding a primary damper to the auxiliary damper or the laminated film.
Because the laminated film is allowed to melt and bonded to the auxiliary damper, the auxiliary damper can be bonded to the primary damper irrespective of the seams, and it will be possible to provide the damper for a speaker which is produced with enhanced workability, and at the same time, free from an irregular adhesion. It is a further effect of the invention that the molds will be less soiled, as compared with the conventional case in which the adhesive has been used. It is a still further effect of the invention that because the auxiliary damper and the primary damper can be simultaneously molded, the production steps will be reduced in number as compared with the conventional case in which the adhesive has been used.
According to a further aspect of the invention, the method further comprises a step of cutting a periphery of the auxiliary damper into a predetermined shape, after the step of laminating the film.
This will eliminate a necessity of attaching the auxiliary damper concentrically to the primary damper so as not to disturb movements of the damper. Therefore, there is no need of cutting the periphery of the auxiliary number in advance, and workability will be enhanced.
According to a still further aspect of the invention, the primary damper is bonded to the auxiliary damper or the laminated film by varying a thickness of the laminated film. Accordingly, even though the molds having clearances have been employed, the areas of the damper having the clearances can be easily bonded, by varying the thickness of the laminate film.
According to a still further aspect of the invention, there is provided a method of producing a damper for a speaker comprising the steps of applying a coating agent on an auxiliary damper which has been impregnated with a thermosetting resin, and bonding a primary damper to the auxiliary damper coated with the coating agent.
Because the coating agent is allowed to melt and bonded to the auxiliary damper, the auxiliary damper can be bonded to the primary damper irrespective of the seams, and it will be possible to provide the damper for a speaker which is produced with enhanced workability, and at the same time, free from an irregular adhesion. It is a further effect of the invention that the molds will be less soiled, as compared with the conventional case in which the adhesive has been used. It is a still further effect of the invention that because the auxiliary damper and the primary damper can be simultaneously molded, the production steps will be reduced in number as compared with the conventional case in which the adhesive has been used.
According to a still further aspect of the invention, the primary damper is bonded to the auxiliary damper by varying a thickness of the coating agent. By thus varying the thickness of the coating agent, even the damper produced with the molds having clearances can be easily bonded.